Secured and Unsecured Debt of the Operating Partnership - Unsecured Term Loan Facility (Details) - USD ($)	6 Months Ended	12 Months Ended
Jun. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Unsecured debt, net	$ 2,097,083,000	$ 1,847,351,000
Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt, net	2,097,083,000	1,847,351,000
Unamortized deferred financing costs	12,000,000
Line of Credit [Member] \| $150 Million Term Loan Facility [Member] \| Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt, net	$ 150,000,000	$ 150,000,000
Debt instrument, interest rate, effective percentage	2.36%	1.85%
Maturity date	Jul. 01, 2019	Jul. 01, 2019
Unamortized deferred financing costs	$ 500,000	$ 700,000
Line of Credit [Member] \| $150 Million Term Loan Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Variable rate (percent)	1.15%
Line of Credit [Member] \| $39 Million Unsecured Term Loan [Member] \| Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unsecured debt, net	$ 39,000,000	39,000,000
Line of Credit [Member] \| $39 Million Unsecured Term Loan [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| Kilroy Realty, L.P. [Member]
Debt Instrument [Line Items]
Unamortized deferred financing costs	$ 100,000	$ 200,000
Variable rate (percent)	1.15%	1.15%

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

+ Details

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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